In a storage apparatus in which storage control apparatuses are redundantly provided (such apparatuses are hereinafter referred to as “redundant modules”), when a problem has occurred at a redundant module, it is sometimes possible to clear the error and recover from the problem by restarting the redundant module. By doing so, it is possible for the storage apparatus to maintain its functionality without the redundant module where the problem occurred needing to be replaced.
On detecting a broken path including a redundant module where an error has occurred, a server apparatus cuts off the path (or “error path”) and switches to a failover path. By doing so, it is possible for the server apparatus to continue accessing the storage apparatus, though there may be some drop in performance due to the loss of one path. When the redundant module where the error occurred has recovered by restarting, the server apparatus can recover from the error that occurred at the redundant module by re-establishing the path that was cut off.
See, for example, the following documents:
Japanese Laid-open Patent Publication No. 2002-169659
Japanese Laid-open Patent Publication No. 2008-204238
Japanese Laid-open Patent Publication No. 2008-217202
However, a server apparatus that accesses storage apparatuses like that described above needs to have a function that switches to a failover path. Since the detecting of a broken path is also carried out by the server apparatus, there is a delay in detecting a broken path, which may cause a drop in responsiveness, which is one of system requirements. On the other hand, erroneous detection of a broken path may destabilize the system. Depending on the system, a system engineer may be requested to make operations to re-establish a path that has been temporarily cut off.